Hello, I'm trying to make a simple webpage with two input text boxes that when submitted when empty, I'll get an error pop-up telling me which ones are empty, both, first name, or last name. When there's only one if, the script works. But when there's multiple else ifs, nothing happens if I press submit. Can someone help me?

You should note that form validation of the pattern if (document.forms[0].elements[1].value == "") is barely worthy of the name, and virtually useless, as even a single space, an X or a ? will return false, that is pass the validation. This topic has been covered many times before in this forum.